## What is the difference between floor flatness and floor levelness?

Floor Flatness (FF): The FF number essentially tells you how flat your concrete floor is. Bumps and grooves cause your Floor Flatness numbers to drop. Higher F-numbers equal flatter floors. Floor Levelness (FL): The FL number indicates if you have any tilts or pitches in the slab.

**How do you measure flatness and levelness of a floor?**

Floor Flatness is measured by tracking the difference in elevation between two points 1 foot apart and comparing them with every other 1-foot elevation change across a measured distance or “run.” Floor Levelness on the other hand compares the change in elevation over a distance of 10 feet, by determining the net change …

**What are FF and FL numbers?**

Ff, or “flatness F-Number,” defines the maximum floor curvature allowed over 24″ (600 mm) computed on the basis of successive 12″ (300 mm) elevation differentials. Fl, or “levelness F-Number,” defines the relative conformity of the floor surface to a horizontal plane as measured over a 10′ (3.03m) distance.

### How are FF and FL numbers calculated?

To calculate FL, add the absolute value of the z mean to three times the standard deviation, then invert the number. Flatness numbers are on a scale of 10 to 150, and most slabs fall in the range of 15 to 100. The minimum FL and FF values needed will depend on the building type.

**How is levelness measured?**

To measure levelness, use the differences, z, in elevation between two points that are 10 feet apart. The mean and standard deviation can then be calculated. To calculate FL, add the absolute value of the z mean to three times the standard deviation, then invert the number.

**How is FF measured?**

FF—This number is used to indicate the flatness of a random-traffic floor. FF is measured as the curvature of the floor over a 2-foot interval. Take a grid of 2-foot intervals over the entire floor and put the values through an equation and you get the FF value as an indication of the waviness of the floor.

#### How is FL and FF measured?

**What is FMIN floor flatness?**

Fmin is actually a direct measurement of the floor surface in the wheel path of the forklift for which the defined traffic area is designed. An Fmin100 specification is a baseline number corresponding to a flatness tolerance of 1/8″ in 10′-0″.

**What does a specification for a floor flatness equal in f-numbers?**

What does a specification for a floor flatness of 1/8 inch in 10 feet equal in F-numbers? A.: Although there are no direct equivalents between F-numbers and straightedge tolerances, ACI 302, “Construction of Concrete Floors and Slabs,” gives the following table of approximate values:

## How do you measure flatness and levelness on a floor?

Flatness and levelness are measured on random traffic floors using a Dipstick. GTS, Inc. On a random-traffic floor, F F /F L should be specified both for the entire floor (overall minimum) and for the area within a single bay (local minimum).

**What does 67% flatness mean on a floor?**

Floor Flatness and Joints. “The overall numbers are for the entire floor; the minimum local values apply to each individual square defined by the sawcuts.”. The minimum-local value is generally specified as 67% of the overall value, which allows a single bay to be slightly less flat and level than the overall floor.

**What does F L mean in floor levelness?**

Floor levelness (F L) controls the departure of the floor surface from the specified slope or plane of the surface. F L numbers evaluate the elevation differences along a sample line at 10-foot intervals. The higher the F L number, the more level the floor.